The disclosed embodiments generally pertain to ceramic matrix composite components for gas turbine engines. More particularly, the present embodiments relate to methods and materials for forming in-situ cavities in ceramic matrix composite components.
In a gas turbine engine, air is pressurized in a compressor and mixed with fuel in a combustor for generating hot combustion gases which flow downstream through turbine stages. A typical gas turbine engine generally possesses a forward end and an aft end with its several core or propulsion components positioned axially therebetween. An air inlet or intake is located at a forward end of the engine. Moving toward the aft end, in order, the intake is followed by a fan, a compressor, a combustion chamber, and a turbine. It will be readily apparent from those skilled in the art that additional components may also be included in the engine, such as, for example, low-pressure and high-pressure compressors, and low-pressure and high-pressure turbines. This, however, is not an exhaustive list.
The compressor and turbine generally include rows of airfoils that are stacked axially in stages. Each stage includes a row of circumferentially spaced stator vanes and a rotor assembly which rotates about a center shaft or axis of the turbine engine. A multi-stage low pressure turbine follows the multi-stage high pressure turbine and is typically joined by a second shaft to a fan disposed upstream from the compressor in a typical turbo fan aircraft engine configuration for powering an aircraft in flight. These turbine stages extract energy from the combustion gases.
The stator is formed by a plurality of nozzle segments which are abutted at circumferential ends to form a complete ring about the axis of the gas turbine engine. Each nozzle segment may comprise one or more vanes which extend between an inner band and an outer band. The stator nozzles direct the hot combustion gas in a manner to maximize extraction at the adjacent downstream turbine blades.
Turbine rotor assemblies typically include at least one row of circumferentially-spaced rotor blades. Each rotor blade includes an airfoil that having a pressure side and a suction side connected together at leading and trailing edges. Each airfoil extends radially outward from a rotor blade platform. Each rotor blade may also include a dovetail that extends radially inward from a shank extending between the platform and the dovetail. The dovetail is used to mount the rotor blade within the rotor assembly to a rotor disc or spool. Known blades are hollow such that an internal cooling cavity is defined at least partially by the airfoil, platform, shank, and dovetail.
Ceramic matrix composite (“CMC”) materials are of particular interest for use in gas turbine engines as higher operating temperatures are sought to increase efficiencies. CMC materials may be used for various components, for example airfoils in the turbine, compressor and fan regions of the engine. CMC materials typically comprise a ceramic fiber reinforcement material embedded in a ceramic matrix material. The reinforcement material aids to provide load-bearing function for the CMC and the ceramic matrix protects the reinforcement material, maintains fiber orientation and dissipates loads to the reinforcement material. Various methods are taught in U.S. Publication No. 2013/0285296 dated 31 Oct. 2013 and U.S. Publication 2014/0072736 dated 13 Mar. 2014, both of which are incorporated by reference herein.
With currently utilized ceramic matrix composite components, features are formed in the parts after molding by subsequent machining. The machining results in removal of material to form the desired feature, for example, cooling apertures. The machined features are limited in design due to the manufacturing process of the machining to remove the material. For example, in a drilling process, the feature is generally limited to straight-line features.
It would be desirable to overcome these and other features and form a molded component with improved geometric features that currently may not be formed utilizing known machining techniques. It is further desirable to decrease or eliminate material removal or clearing steps currently required in prior art molding techniques.